Autoradiography is a technique for tracking the movement and location in living cells of a component or building block, which is labeled with a radioactive isotope, of a compound which is important to cell life and function such as DNA, RNA, or an enzyme. The component or building block which is labeled with the radioactive isotope is, during the usual function of the cell, incorporated into an essential cell constituent such as RNA, DNA or an enzyme. The rate of incorporation of the labeled building block or component into the cell is a measure of the activity of that cell which provides useful physiological information which is valuable in clinical research and medicine.
Among the important cell constituents which can be followed in this fashion are DNA and RNA. The rate of production of DNA or RNA in a living cell is a measure of the physiological activity of that cell and provides data which may indicate whether that cell may be normal or abnormal. For example, cells of malignant tissues have abnormal growth kinetics and may have disturbed DNA and/or RNA turnover. By measuring the production of DNA or RNA through a radioactive isotope-labeled component of DNA or RNA such as tritiated thymidine or tritiated uridine, it is possible to determine the activity of the cell and thus get useful information which will aid in determining whether the cell is malignant or normal and, if malignant, whether it would be subject to chemotherapeutic treatment.
Autoradiography enables a physiologist to determine, for example, which cells of a tissue are synthesizing DNA or RNA at a normal or rapid rate and how much of these materials are produced per cell. From such data, it is possible to determine whether the tissue containing the cells under investigation may be susceptible to chemotherapy which interferes with cell growth.
In the practice of autoradiography, tissues under examination are broken down into a suspension of living cells. The suspension of cells under evaluation is incubated with the tritiated isotope, such as tritiated thymidine or tritiated uridine. The synthesis of DNA or RNA by those cells can be evaluated in terms of the rate and amount of isotope incorporated. The DNA or RNA which contains the radioactive thymidine or uridine are thus labeled with a radioactive isotope (tritium) and can be traced or tracked through normal physiological processes by radioactive tracking procedures. Through such techniques, it is possible to obtain accurate data relative to the production of DNA or RNA by the cells under investigation. The same techniques can be used in studying the kinetics of other cell constituents.